Internal combustion engines that operate on air as the gas of the gas-fuel mixture emit combustion by-products including NOx, CO, hydrocarbons, particles, etc. Accordingly, internal combustion engines, e.g., such as those used to power vehicles, include emissions after-treatment equipment to eliminate or reduce such by-products.
The enrichment of air with oxygen for the gas of the gas-fuel mixture can virtually eliminate soot emissions and can significantly reduce CO and hydrocarbon emissions. The type of enrichment of air with oxygen can increase NOx emissions. However, the use of substantially pure oxygen as the gas of the gas-fuel mixture can achieve a near-zero emissions of NOx.